September 27, 2012

Competing Regions in Brain Impact Diet Choices

Researchers from the California Institute of Technology (Caltech) recently discovered that an individual´s internal struggle to choose between healthy and unhealthy food items is based off of neural processes in the brain.

"We seem to have independent systems capable of guiding our decisions, and in situations like this one, these systems may compete for control of what we do," explained the study´s lead author Cendri Hutcherson, a Caltech postdoctoral scholar, in the prepared statement.

The researchers believe that this self-regulation can make or break a person´s choice to eat something that is fattening.

"In many cases, these systems guide behavior in the same direction, so there's no conflict between them," continued Hutcherson in the statement. "But in other cases, like the all-too-common inner fight to resist the temptation of eating the chocolate cake, they can guide behavior toward different outcomes. Furthermore, the outcome of the decision seems to depend on which of the two systems takes control of behavior."

The scientists believe that there is much evidence that highlights how the decision making process of individuals is affected by different values placed on a group of provided options. In effect, people make a decision based on whichever choice has the highest value. With a “single-value hypothesis,” someone could make the choice between something that is tasty and unhealthy versus something that has so-so taste but is not as fattening. On the other hand, the “multiple-value hypothesis” states that there are multiple systems with various values and so the brain will choose the healthy option when the brain turns on the system that measures healthiness.

"An important and controversial open question–which this study was designed to address–is whether there is a single value signal in the brain, or if there are instead multiple value signals with different properties that compete for the control of behavior," remarked Antonio Rangel, a professor of economics and neuroscience at Caltech, in the statement.

The study included 26 volunteers who were required to not consume any food for four hours before the test was conducted. The scientists used a functional magnetic resonance imaging (fMRI) machine during the exam to determine the brain activity of participants when they were asked how much they were willing to pay for a particular snack. The volunteers had to choose the snack when they were acting normally, when they were focused on limiting their desire of eating, and when they were intent on increasing their desire to feast on the snack. The researchers allowed the participants to do whatever necessary to keep a semblance of self-control, be it by thinking about the taste of the snack or by focusing on the healthiness of the food. The individuals then placed real bids to buy the food after waiting for four seconds.

Based on the results, the researchers discovered that there were two areas in the brain that focused on when the individuals wanted a particular item. The dorsolateral prefrontal cortex (dlPFC) and the ventromedial prefrontal cortex were found to have different roles when the participants were trying to control their hunger. The dlPFC was the area that focused on not wanting the food, while the vmPFC was the area that focused on desiring the snack.

Furthermore, the team of investigators found that the change between the two different parts of the brain did not happen instantaneously. The brain had to take a few seconds before being able to change from the dlPFC to the vmPFC. Researchers in the past have observed dieters, but the results have shown that only the vmPFC controls the decision making process. Connecting in the new findings to the results of the old study, the scientists suggest that dieters are more used to self-control and that people who practice dieting may gain more ability in self-regulation.

"This research suggests a reason why it feels so difficult to control your behavior," concluded Hutcherson in the statement. "You've got these really fast signals that say, go for the tempting food. But only after you start to go for it are you able to catch yourself and say, no, I don't want this."